inner beans detected as ApplicationListeners as well (SPR-6049)

Author: jhoeller

org.springframework.context/src/main/java/org/springframework/context/ConfigurableApplicationContext.java

@@ -99,8 +99,8 @@ public interface ConfigurableApplicationContext extends ApplicationContext, Life
 	 * Add a new ApplicationListener that will be notified on context events
 	 * such as context refresh and context shutdown.
 	 * <p>Note that any ApplicationListener registered here will be applied
-	 * on refresh of this context. If a listener is added after the initial
-	 * refresh, it will be applied on next refresh of the context.
+	 * on refresh if the context is not active yet, or on the fly with the
+	 * current event multicaster in case of a context that is already active.
 	 * @param listener the ApplicationListener to register
 	 * @see org.springframework.context.event.ContextRefreshedEvent
 	 * @see org.springframework.context.event.ContextClosedEvent

org.springframework.context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -20,11 +20,14 @@
 import java.lang.annotation.Annotation;
 import java.security.AccessControlException;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Date;
 import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Set;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -193,7 +196,7 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 	private ApplicationEventMulticaster applicationEventMulticaster;
 
 	/** Statically specified listeners */
-	private List<ApplicationListener> applicationListeners = new ArrayList<ApplicationListener>();
+	private Set<ApplicationListener> applicationListeners = new LinkedHashSet<ApplicationListener>();
 
 
 	/**
@@ -362,13 +365,18 @@ public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
 	}
 
 	public void addApplicationListener(ApplicationListener listener) {
-		this.applicationListeners.add(listener);
+		if (isActive()) {
+			addListener(listener);
+		}
+		else {
+			this.applicationListeners.add(listener);
+		}
 	}
 
 	/**
 	 * Return the list of statically specified ApplicationListeners.
 	 */
-	public List<ApplicationListener> getApplicationListeners() {
+	public Collection<ApplicationListener> getApplicationListeners() {
 		return this.applicationListeners;
 	}
 
@@ -817,7 +825,7 @@ protected void registerListeners() {
 		// Do not initialize FactoryBeans here: We need to leave all regular beans
 		// uninitialized to let post-processors apply to them!
 		String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
-		for (final String lisName : listenerBeanNames) {
+		for (String lisName : listenerBeanNames) {
 			getApplicationEventMulticaster().addApplicationListenerBean(lisName);
 		}
 	}

org.springframework.context/src/main/java/org/springframework/context/support/ApplicationContextAwareProcessor.java

@@ -19,11 +19,18 @@
 import java.security.AccessControlContext;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 
 import org.springframework.beans.BeansException;
-import org.springframework.beans.factory.config.BeanPostProcessor;
+import org.springframework.beans.factory.support.MergedBeanDefinitionPostProcessor;
+import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.ApplicationEventPublisherAware;
+import org.springframework.context.ApplicationListener;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.MessageSourceAware;
 import org.springframework.context.ResourceLoaderAware;
@@ -48,10 +55,14 @@
  * @see org.springframework.context.ApplicationContextAware
  * @see org.springframework.context.support.AbstractApplicationContext#refresh()
  */
-class ApplicationContextAwareProcessor implements BeanPostProcessor {
+class ApplicationContextAwareProcessor implements MergedBeanDefinitionPostProcessor {
+
+	private final Log logger = LogFactory.getLog(getClass());
 
 	private final ConfigurableApplicationContext applicationContext;
 
+	private final Map<String, Boolean> singletonNames = new ConcurrentHashMap<String, Boolean>();
+
 
 	/**
 	 * Create a new ApplicationContextAwareProcessor for the given context.
@@ -61,7 +72,13 @@ public ApplicationContextAwareProcessor(ConfigurableApplicationContext applicati
 	}
 
 
-	public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
+	public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class beanType, String beanName) {
+		if (!this.applicationContext.containsBean(beanName) && beanDefinition.isSingleton()) {
+			this.singletonNames.put(beanName, Boolean.TRUE);
+		}
+	}
+
+	public Object postProcessBeforeInitialization(final Object bean, final String beanName) throws BeansException {
 		AccessControlContext acc = null;
 
 		if (System.getSecurityManager() != null &&
@@ -73,19 +90,19 @@ public Object postProcessBeforeInitialization(final Object bean, String beanName
 		if (acc != null) {
 			AccessController.doPrivileged(new PrivilegedAction<Object>() {
 				public Object run() {
-					doProcess(bean);
+					doProcess(bean, beanName);
 					return null;
 				}
 			}, acc);
 		}
 		else {
-			doProcess(bean);
+			doProcess(bean, beanName);
 		}
 
 		return bean;
 	}
 
-	private void doProcess(Object bean) {
+	private void doProcess(Object bean, String beanName) {
 		if (bean instanceof ResourceLoaderAware) {
 			((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
 		}
@@ -98,6 +115,27 @@ private void doProcess(Object bean) {
 		if (bean instanceof ApplicationContextAware) {
 			((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
 		}
+
+		if (bean instanceof ApplicationListener) {
+			if (!this.applicationContext.containsBean(beanName)) {
+				// not a top-level bean - not detected as a listener by getBeanNamesForType retrieval
+				Boolean flag = this.singletonNames.get(beanName);
+				if (Boolean.TRUE.equals(flag)) {
+					// inner singleton bean: register on the fly
+					this.applicationContext.addApplicationListener((ApplicationListener) bean);
+				}
+				else if (flag == null) {
+					// inner bean with other scope - can't reliably process events
+					if (logger.isWarnEnabled()) {
+						logger.warn("Inner bean '" + beanName + "' implements ApplicationListener interface " +
+								"but is not reachable for event multicasting by its containing ApplicationContext " +
+								"because it does not have singleton scope. Only top-level listener beans are allowed " +
+								"to be of non-singleton scope.");
+					}
+					this.singletonNames.put(beanName, Boolean.FALSE);
+				}
+			}
+		}
 	}
 
 	public Object postProcessAfterInitialization(Object bean, String name) {

org.springframework.context/src/test/java/org/springframework/context/event/ApplicationContextEventTests.java

@@ -25,6 +25,7 @@
 import static org.junit.Assert.*;
 import org.junit.Test;
 
+import org.springframework.beans.TestBean;
 import org.springframework.beans.factory.config.RuntimeBeanReference;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.ApplicationContext;
@@ -126,6 +127,19 @@ public void listenerAndBroadcasterWithCircularReference() {
 		assertEquals("The event was not received by the listener", 2, broadcaster.receivedCount);
 	}
 
+	@Test
+	public void innerBeanAsListener() {
+		StaticApplicationContext context = new StaticApplicationContext();
+		RootBeanDefinition listenerDef = new RootBeanDefinition(TestBean.class);
+		listenerDef.getPropertyValues().addPropertyValue("friends", new RootBeanDefinition(BeanThatListens.class));
+		context.registerBeanDefinition("listener", listenerDef);
+		context.refresh();
+		context.publishEvent(new MyEvent(this));
+		context.publishEvent(new MyEvent(this));
+		TestBean listener = context.getBean(TestBean.class);
+		assertEquals(3, ((BeanThatListens) listener.getFriends().iterator().next()).getEventCount());
+	}
+
 
 	public static class MyEvent extends ApplicationEvent {